The traditional implantable cardiac pacemaker includes a pulse generator device to which one or more flexible elongate lead wires are coupled. The device is typically implanted in a subcutaneous pocket, remote from the heart, and each of the one or more lead wires extends therefrom to a corresponding electrode, coupled thereto and positioned at a pacing site, either endocardial or epicardial. Mechanical complications and/or MRI compatibility issues, which are sometimes associated with elongate lead wires and well known to those skilled in the art, have motivated the development of implantable cardiac pacing devices that are wholly contained within a relatively compact package, the entirety of which is configured for implant in close proximity to a pacing site. Such a relatively compact intra-cardiac device configured for dual chamber pacing may be implanted as shown in the schematic diagram of FIG. 1. FIG. 1 illustrates a dual chamber intra-cardiac pacing device including a first portion 10 implanted in a right ventricle RV of a heart, in proximity to an apex thereof, and a second portion 20 implanted in a right atrium RA of the heart, within an appendage 102 thereof. FIG. 1 further illustrates the device including a leadlet 12 that connects first portion 10 to second portion 20. There is a need for improved interventional medical systems facilitating the implant of relatively compact intra-cardiac dual chamber pacing devices like that illustrated in FIG. 1.